FATIGABILITY DIFFERS BETWEEN THE SHOULDER AND LEGS AND IS MODERATED BY AGE

Yoon, T., Senefeld, J., Bement, M. H., & Hunter, S. K. (2012). Age differences in fatigue during dynamic contractions in arm and leg muscles. Presentation 1015 at the 59th Annual Meeting of the American College of Sports Medicine, San Francisco, California; May 29-June 2, 2012.

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This study compared muscular fatigue in young (M = 15; F = 13; ~22 years) and old (M = 4; F = 3; ~76 years) adults during repeated maximal voluntary dynamic contractions with a submaximal load at maximal velocity (MVDC) in arm and leg muscles. Ss attended two sessions to test dynamic fatigue of the elbow flexor and knee extensor muscles on the Biodex System 4 Pro dynamometer. For each MVDC, Ss moved their limbs concentrically through a 90 range of motion at maximal velocity with a load equivalent to 20% of maximal voluntary isometric contraction force. This cycle was repeated every three seconds for three sets of 30 contractions. Maximal voluntary isometric contractions were performed at the start of the session and immediately after each set of 30 contractions.

Young adults were stronger than old adults in both elbow flexion and knee extension. The relative decline in maximal voluntary isometric contraction force was greater for young adults than old adults in elbow flexion but similar in knee extension. The relative decline in maximal voluntary isometric contraction was greater in the elbow flexors than the knee extensors. Maximal contraction speed was faster for young adults than old adults in knee extension but similar in elbow flexion. Maximal contraction speed during MVDC decreased with the fatiguing contractions in both sessions. The relative decline was greater for old adults in knee extension but similar in elbow flexion. The relative decline was greater for the elbow flexors than the knee extensors.

Implication. When fatigue is induced by a dynamic contraction at maximal voluntary speed with a submaximal load: 1) the age difference in the fatigue of the elbow and knee extensor muscles varies depending on the measurement task; and 2) the elbow flexor muscles are more fatigable than knee extensors.

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